As a child, Collier was introduced to the work of Robert Crumb, whose work has been a significant influence. (Collier's cross-hatching style is particularly reminiscent of Crumb's work.) Before breaking into comics, Collier served in the Canadian Army, where (among other activities) he drew comic strips for the army newspapers. His Army training also introduced him to long-distance running and the biathlon, in which he has competed nationally.

His first comic strip was published in 1986 in the R. Crumb-edited magazine Weirdo, and his work has been published in numerous other comics anthologies, including Duplex Planet Illustrated, Drawn and Quarterly, The Comics Journal, and Zero Zero; as well as Harvey Pekar's American Splendor, most notably the three-issue American Splendor: Unsung Hero. Since 1990, Collier has also done comics and illustrations for Canadian newspapers such as The Globe and Mail and the Saskatoon StarPhoenix.

Fantagraphics published four issues of the aptly-titled series Collier's in the early 1990s. Most of the material from his anthology submissions as well as Collier's was collected in Just The Facts (Drawn and Quarterly, 1998), a comprehensive look back at a decade's-worth of his "comic strip essays". In 2002, Drawn and Quarterly began publishing volume two of Collier's solo comic book title Collier's.

Collier's Surviving Saskatoon (D&Q, 2000) documents the true story of David Milgaard, a man who spent nearly 25 years in prison after he was wrongfully accused of the brutal rape and murder of a nurse in 1969.

Collier lives with his wife, Ontario artist Jennifer Hambleton, and son James (born in 1999), in Hamilton.

Collier's The Frank Ritza Papers was nominated for a Doug Wright Award for Best Book in 2005.